Ions/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby. Tim is sitting at a dinner table. Seated next to him is Moby Tim is wearing a T-shirt that shows a schematic diagram of an atom, showing a center nucleus with electrons circling it in rings. Tim has a plate of food in front of him. He is holding a salt shaker and trying to pour salt on his food but no salt is coming out. TIM: How come there's never any salt? MOBY: Beep. Moby shrugs and hands Tim a sheet of paper. Tim reads from a typed letter. TIM: Dear Tim and Moby, I have to do a project about ions. Can you tell me about them? From Kaitlynne. Hey there. An ion is an atom that has an electrical charge. MOBY: Beep? TIM: Yeah, we should probably do a quick review of atoms. You probably know that atoms have a nucleus made up of neutrons and protons. A picture shows a stylized view of the nucleus of an atom. There are a number of spheres tightly packed together. Some are colored yellow and some are colored orange. As we zoom in, labels appear, identifying these as neutrons and protons. TIM: Protons have a positive charge, and neutrons have no charge. As Tim mentions the "positive charge", a plus sign flashes on the screen and half the spheres flash pink in color. As Tim mentions "no charge", a symbol flashes on the screen that looks like a zero with a slash through it and the other half of the spheres flash blue in color. TIM: For every proton, an atom has one electron, a negatively charged particle that orbits the nucleus. The view of the nucleus zooms out and we see three rings around it. There are small blue circles on each ring. The innermost ring has two blue circles. The next ring has eight blue circles and the outer ring also has eight blue circles. The label "electron" appears on the screen. The blue circles are rotating around the nucleus. TIM: Because of the equal number of electrons and protons, atoms have no charge. Various views show that the blue circles are moving in three dimensions and not just in flat circular planes as they circle the nucleus. TIM: The negative electrons and positive protons cancel each other out. But if an atom loses or gains an electron, then that balance is lost, and the atom becomes a charged ion. Various particles are shown moving around the nucleus. The caption "ion" appears. MOBY: Beep? TIM: Well, an atom's electrons orbit the nucleus in energy levels called shells. Each shell can hold a certain number of electrons, starting with two in the first shell, eight in the second, and ending up with a maximum of 32 per shell. The previous figure returns, showing a nucleus of tightly packed yellow and orange spheres surrounded by three rings. The rings contain blue dots. The caption now reads "shells". TIM: The outer electron shell is called the valence shell. The label "valence shell" appears near the outermost circle. TIM: Atoms like to have a full valence shell. So atoms with nearly empty valence shells will often give up their valence electrons, becoming positively-charged cations. A new atom slides into view. This one has two full inner shells with two and eight electrons, respectively. The outermost shell has only one electron. The single electron is then seen moving off screen, leaving a nucleus with two full shells. The circle representing the empty shell disappears and the label "cations" appears. TIM: Atoms with nearly full valence shells often take on extra electrons, becoming negatively-charged anions. A new atom slides into view. This one has two full inner shells with two and eight electrons, respectively. The outermost shell has seven electrons. Another electron is then seen moving in from off-screen and entering the outermost shell. The outermost shell is now full with eight electrons and the label "anions" appears. TIM: That's why atoms that like to lose electrons are said to have positive valence, and atoms that like to gain electrons have negative valence. On the periodic table, positive valence atoms tend to be grouped on the left. A table appears labeled "The periodic table of elements." It shows the abbreviations for the names of all the different types of elements. They are numbered from 1 to 118. The number of elements in each row grows larger as you proceed down the table, with 3 elements in the first row, 8 elements in the second row, 8 in the third row, 18 in the next row, and so on. Further vertical groupings can be seen by color coding in the columns of the table. As Tim refers to positive valence atoms, the picture zooms into the left side of the table showing elements with numbers 1, 3, 4, 11, 12, 19, and 20. TIM: On the right side of the table, atoms tend to have a negative valence. The figure pans to the right side of the table and we now see a close-up of elements with numbers 2, 5 through 10, and 13 through 18. TIM: Let's look at a specific example. A small diagram of an atom appears behind Moby. It grows larger and larger and eventually knocks him down and he falls off screen. The diagram is now as large as the figure of Tim and is labeled "Sodium". It consists of the symbol "Upper N a" in the center with three circular rings around it. The innermost ring contains two black circles. The middle ring has eight black circles and the outermost ring contains just one black circle. There are a total of eleven black circles and the numeral "eleven" appears in large print underneath the word "Sodium". TIM: Whoa, déjà vu. Ah, anyway... sodium has eleven electrons, giving it one valence electron. Tim picks up a pointer and points at the lone black circle in the outermost ring. TIM: It doesn't take much energy to knock off that lone electron, which means that there are a lot of positively-charged sodium ions floating around. An enlarged view appears with the label "Upper N a" in the center. The same three rings are around it with just one electron in the outermost ring. A hand comes into view and, with a flick of a finger, knocks that lone electron away. The legend changes to "Upper N a plus". TIM: Chlorine has 17 electrons, with seven valence electrons instead of a complete eight. A new figure of an atom slides into view. At the center is the label "Upper C l". There are three rings of electrons around it. The innermost ring shows two electrons. The next ring shows eight electrons. The outermost ring shows seven electrons. TIM: So it likes to scoop up an extra electron, resulting in negative chlorine ions. Another electron floats into view and takes a place in the outermost ring, which now has eight electrons. The interior label changes to "Upper C l minus". TIM: Since the two ions have different charges, they're often drawn together, kind of like two poles of a magnet. Both atoms are now shown; the one with the label "Upper N a plus" and the one with the label "Upper C l minus". They move toward each other until their outermost rings touch. The scene then shifts back to Tim and Moby at the kitchen table. Tim is refilling the empty salt shaker from a container labeled "salt". MOBY: Beep? TIM: Yep, they become the uncharged sodium chloride: table salt. The ionic bond holding salt together is pretty strong when it's on your table. But as soon as it's put into water, the electrical forces in the water dissolve the bond. A close-up now shows Moby pouring the salt from the salt shaker into a container of water. The picture zooms in until we see atoms floating around in the water. They are moving apart from each other. Zoom back out to Tim and Moby at the kitchen table. Moby is done drinking. TIM: Is...is that where all the salt is going? Moby hands Tim the salt shaker. Tim tries to use it on his food but discovers that the salt shaker is now empty. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts